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Planet Directly Observed Orbiting Distant Star

This false-color near-infrared image has been processed to remove most of the scattered light from the star Kappa Andromedae (masked out at center).The “super-Jupiter” companion, Kappa Andromedae b (upper left), lies at a projected distance of about 55 times the average distance between Earth and the sun and about 1.8 times farther than Neptune, whose orbit is shown for comparison (dashed circle). Image Credit: NOAJ/Subaru/J. Carson, College of Charleston

Astronomers have discovered a possible, and huge, planet orbiting a distant star utilizing the Subaru Telescope in Hawaii. The star, Kappa Andromedae, now goes into the record books as the most massive star that is known to have a planet orbiting it. 

This discovery was due, in large part, to the Subaru Telescope’s adaptive optics which employs equipment that compensates for Earth’s thick atmosphere. One of the problems with earth-based astronomy is that the gases that blanket our world “smears” what astronomers see. In this case, Subaru’s High Contrast Instrument for the Subaru Next Generation Adaptive Optics and Infrared Camera and Spectrograph defeated the smearing.

Given the size of the object observed orbiting the star, it might not be a planet, but rather a lightweight brown dwarf companion (a very tiny star). Whatever it is, it has already gained a new moniker—Kappa Andromedae b (Kappa And b, for short). This possible planet puts the largest planet in our solar system, Jupiter, to shame.

Kappa And b has been estimated to have a mass approximately 12.8 times greater than Jupiter’s. The immense size of this object is why astronomers are not quite sure on which side of the planet/star divide that Kappa And b falls on.

In this artist’s rendering, Kappa Andromeda b orbits its parent star at nearly twice the distance that Neptune orbits our own sun. Scientists have determined that the planet is about 12.8 times the mass of Jupiter and is bright red in color. Image Credit: NASA’s Goddard Space Flight Center/S. Wiessinger

“According to conventional models of planetary formation, Kappa And b falls just shy of being able to generate energy by fusion, at which point it would be considered a brown dwarf rather than a planet,” said Michael McElwain, a member of the discovery team at NASA’s Goddard Space Flight Center. “But this isn’t definitive, and other considerations could nudge the object across the line into brown dwarf territory.”

Jupiter emits twice the amount of energy that it receives from the sun, and it is unclear if the energy it produces is residual energy left over from the planet’s formation, energy imparted on it from its supersonic rotation (despite its size Jupiter’s day is only ten hours long), or from some other, as yet unknown, process. In the case of Kappa And b, it would be dubbed a star if it was large enough to produce energy by fusing a heavy form of hydrogen known as deuterium.

So how large (or small as is the case) does an object have to be before this is theorized to begin? Thirteen times the size of Jupiter—meaning that Kappa And b is probably just a tad small for this process to begin.

“Kappa And b, the previously imaged planets around HR 8799 and Beta Pictoris, and the most massive planets discovered by non-imaging techniques likely all represent a class of object that formed in much the same way as lower-mass exoplanets,” said lead researcher Joseph Carson, an astronomer at the College of Charleston, S.C., and the Max Planck Institute for Astronomy in Heidelberg, Germany.

Kappa And b allows researchers to study not only aspects of planetary formation, but theoretical limits between planets and stars as well.

Young stars are a prime target for astronomers, as any possible planets orbiting them might not have had enough time to lose the heat from their formation—heat that can be detected in the infrared. Kappa Andromedae became a target when observers estimated its age and found it to be a relatively new star (only an estimated 30 million years old).

Want to see a star that is known to have a planet? This chart allows you to spot Kappa Andromeda. Image Credit: NASA’s Goddard Space Flight Center/DSS

Kappa Andromedae is about 170 light-years away from our own solar system—located in the constellation Andromeda—and it can be seen with the naked eye.

As for Kappa And b itself, the planet has a temperature of some 2,600 degrees Fahrenheit (1,400 Celsius) and is estimated to be about 1.8 times more distant from its star than the planet Neptune is from our sun. If you could see the planet, it would appear reddish in color.

Kappa And b was detected during four separate observations by Carson’s team. Studying Kappa Andromeda’s infrared wavelengths in January and July of this year, the team discovered that both the star and Kappa And b moved across the sky together, proving that they are locked in a gravitational dance.

It is extremely difficult to directly image planets around their parent star as, normally, tiny and therefore dim objects are obscured by the star’s glare. Kappa And b was discovered by studying light in the near-infrared spectrum.

Kappa And b was discovered by a team working under the Strategic Explorations of Exoplanets and Disks with Subaru (SEEDS). This five-year project has been focused toward directly imaging extrasolar planets and protoplanetary disks around distant suns using the Subaru Telescope located at Mauna Kea, Hawaii.

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